setting-the patient self-administers narcotics into the systemic circulation contingent on a button-press. To a behavioral pharmacologist, PCA is a novel form of drug self-administration, a behavior that may be responsive to a whole host of variables. We propose to conduct an experimental analysis of the PCA methodology by bringing it into the laboratory, where such critical variables as drug dose, route of administration and patient characteristics can be closely controlled. In this application we propose to use a well-tested model of tonic pain, the cold pressor test, to address two questions about the PCA methodology. First, is the self-administration of narcotics related to the context in which the drug is available? There is a continued reticence on the part of medical caregivers to administer adequate amounts of opiates, and on the part of patients to use adequate amounts of opiates, in a postoperative setting, for fear of patient addiction. We predict that opiates will indeed function as a reinforcer in non-drug abusing volunteers, but only in a limited context - when the volunteers are in pain. We believe that such a finding, obtained in the laboratory, will have direct clinical relevance to the medical care community. This finding, in conjunction with clinical data already collected, may help dispel the myth that mere exposure to opiates leads to drug addiction, drug seeking, and drug craving. The second question we propose to ask about PCA deals with the issue of the importance of the contingency between the drug-taking response (e.g., a button press) and the administration of a drug. There is a fascinating literature from the animal behavioral pharmacology laboratory that may have direct bearing on PCA and its effectiveness. When an animal has active control over drug administration (i.e., a response produces a drug infusion), as opposed to non-contingent drug administration (i.e., the experimenter administers the drug), different biochemical and neurological events are realized. In other words, whether drug administration is response-contingent (as in PCA) or response- independent (as in the more traditional approach of patient analgesia, 'prn') can affect the biochemical effects of the drug. We will ask the question of whether the degree of pain reduction, or analgesia, is affected as a function of who has control over drug administration - the volunteer or the experimenter. We predict there will be greater analgesia when the subject has control over the drug administration. Such a finding, obtained in the laboratory, would again have direct clinical relevance, and may explain why pain ratings are typically lower and patient satisfaction ratings are typically higher with PCA than with prn narcotic administration.